Method for controlling electric boost in a hybrid powertrain

ABSTRACT

A powertrain system includes an engine coupled to an input member of a transmission operative to transmit power between the input member, a torque machine and an output member. The torque machine is connected to an energy storage device. The engine is selectively operative in engine states comprising an engine-on state and an engine-off state. A method for controlling a powertrain system includes determining a first power range for output power of the energy storage device, commanding the engine to transition from a first engine state to a second engine state, and expanding the first power range of the energy storage device and controlling the torque machine based upon the expanded power range of the energy storage device during the transition from the first engine state to the second engine state.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No.60/985,634 filed on Nov. 5, 2007 which is hereby incorporated herein byreference.

TECHNICAL FIELD

This disclosure is related to managing electric power within powertrainsystems.

BACKGROUND

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Known powertrain architectures include torque-generative devices,including internal combustion engines and electric machines, whichtransmit torque through a transmission device to an output member. Oneexemplary powertrain includes a two-mode, compound-split,electromechanical transmission which utilizes an input member forreceiving motive torque from a prime mover power source, preferably aninternal combustion engine, and an output member. The output member canbe operatively connected to a driveline for a motor vehicle fortransmitting tractive torque thereto. Electric machines, operative asmotors or generators, generate a torque input to the transmission,independently of a torque input from the internal combustion engine. Theelectric machines may transform vehicle kinetic energy, transmittedthrough the vehicle driveline, to electrical energy that is storable inan electrical energy storage device. A control system monitors variousinputs from the vehicle and the operator and provides operationalcontrol of the powertrain, including controlling transmission operatingstate and gear shifting, controlling the torque-generative devices, andregulating the electrical power interchange among the electrical energystorage device and the electric machines to manage outputs of thetransmission, including torque and rotational speed.

SUMMARY

A powertrain system includes an engine coupled to an input member of atransmission operative to transmit power between the input member, atorque machine and an output member. The torque machine is connected toan energy storage device. The engine is selectively operative in enginestates comprising an engine-on state and an engine-off state. A methodfor controlling a powertrain system includes determining a first powerrange for output power of the energy storage device, commanding theengine to transition from a first engine state to a second engine state,and expanding the first power range of the energy storage device andcontrolling the torque machine based upon the expanded power range ofthe energy storage device during the transition from the first enginestate to the second engine state.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of an exemplary powertrain, in accordancewith the present disclosure;

FIG. 2 is a schematic flow diagram of an exemplary architecture for acontrol system and powertrain, in accordance with the presentdisclosure;

FIGS. 3 and 4 are schematic flow diagrams of a control systemarchitecture, in accordance with the present disclosure; and

FIGS. 5 and 6 is a graphical depiction of input and output signals of acontrol system over time, in accordance with the present disclosure.

DETAILED DESCRIPTION

Referring now to the drawings, wherein the showings are for the purposeof illustrating certain exemplary embodiments only and not for thepurpose of limiting the same, FIGS. 1 and 2 depict an exemplary hybridpowertrain. The exemplary hybrid powertrain in accordance with thepresent disclosure is depicted in FIG. 1, comprising a two-mode,compound-split, electromechanical hybrid transmission 10 operativelyconnected to an engine 14 and first and second electric machines(‘MG-A’) 56 and (‘MG-B’) 72. The engine 14 and first and second electricmachines 56 and 72 each generate power which can be transferred to thetransmission 10. The power generated by the engine 14 and the first andsecond electric machines 56 and 72 and transferred to the transmission10 is described in terms of input and motor torques, referred to hereinas T_(I), T_(A), and T_(B) respectively, and speed, referred to hereinas N_(I), N_(A), and N_(B), respectively.

The exemplary engine 14 comprises a multi-cylinder internal combustionengine selectively operative in several states to transfer torque to thetransmission 10 via an input shaft 12, and can be either aspark-ignition or a compression-ignition engine. The engine 14 includesa crankshaft (not shown) operatively coupled to the input shaft 12 ofthe transmission 10. A rotational speed sensor 11 monitors rotationalspeed of the input shaft 12. Power output from the engine 14, comprisingrotational speed and engine torque, can differ from the input speedN_(I) and the input torque T_(I) to the transmission 10 due to placementof torque-consuming components on the input shaft 12 between the engine14 and the transmission 10, e.g., a hydraulic pump (not shown) and/or atorque management device (not shown).

The exemplary transmission 10 comprises three planetary-gear sets 24, 26and 28, and four selectively engageable torque-transferring devices,i.e., clutches C1 70, C2 62, C3 73, and C4 75. As used herein, clutchesrefer to any type of friction torque transfer device including single orcompound plate clutches or packs, band clutches, and brakes, forexample. A hydraulic control circuit 42, preferably controlled by atransmission control module (hereafter ‘TCM’) 17, is operative tocontrol clutch states. Clutches C2 62 and C4 75 preferably comprisehydraulically-applied rotating friction clutches. Clutches C1 70 and C373 preferably comprise hydraulically-controlled stationary devices thatcan be selectively grounded to a transmission case 68. Each of theclutches C1 70, C2 62, C3 73, and C4 75 is preferably hydraulicallyapplied, selectively receiving pressurized hydraulic fluid via thehydraulic control circuit 42.

The first and second electric machines 56 and 72 preferably comprisethree-phase AC machines, each including a stator (not shown) and a rotor(not shown), and respective resolvers 80 and 82. The motor stator foreach machine is grounded to an outer portion of the transmission case68, and includes a stator core with coiled electrical windings extendingtherefrom. The rotor for the first electric machine 56 is supported on ahub plate gear that is operatively attached to shaft 60 via the secondplanetary gear set 26. The rotor for the second electric machine 72 isfixedly attached to a sleeve shaft hub 66.

Each of the resolvers 80 and 82 preferably comprises a variablereluctance device including a resolver stator (not shown) and a resolverrotor (not shown). The resolvers 80 and 82 are appropriately positionedand assembled on respective ones of the first and second electricmachines 56 and 72. Stators of respective ones of the resolvers 80 and82 are operatively connected to one of the stators for the first andsecond electric machines 56 and 72. The resolver rotors are operativelyconnected to the rotor for the corresponding first and second electricmachines 56 and 72. Each of the resolvers 80 and 82 is signally andoperatively connected to a transmission power inverter control module(hereafter ‘TPIM’) 19, and each senses and monitors rotational positionof the resolver rotor relative to the resolver stator, thus monitoringrotational position of respective ones of first and second electricmachines 56 and 72. Additionally, the signals output from the resolvers80 and 82 are interpreted to provide the rotational speeds for first andsecond electric machines 56 and 72, i.e., N_(A) and N_(B), respectively.

The transmission 10 includes an output member 64, e.g. a shaft, which isoperably connected to a driveline 90 for a vehicle (not shown), toprovide output power to the driveline 90 that is transferred to vehiclewheels 93, one of which is shown in FIG. 1. The output power at theoutput member 64 is characterized in terms of an output rotational speedN_(O) and an output torque T_(O). A transmission output speed sensor 84monitors rotational speed and rotational direction of the output member64. Each of the vehicle wheels 93 is preferably equipped with a sensor94 adapted to monitor wheel speed, V_(SS-WHL), the output of which ismonitored by a control module of a distributed control module systemdescribed with respect to FIG. 2, to determine vehicle speed, andabsolute and relative wheel speeds for braking control, tractioncontrol, and vehicle acceleration management.

The input torque from the engine 14 and the motor torques from the firstand second electric machines 56 and 72 (T_(I), T_(A), and T_(B)respectively) are generated as a result of energy conversion from fuelor electrical potential stored in an electrical energy storage device(hereafter ‘ESD’) 74. The ESD 74 is high voltage DC-coupled to the TPIM19 via DC transfer conductors 27. The transfer conductors 27 include acontactor switch 38. When the contactor switch 38 is closed, undernormal operation, electric current can flow between the ESD 74 and theTPIM 19. When the contactor switch 38 is opened electric current flowbetween the ESD 74 and the TPIM 19 is interrupted. The TPIM 19 transmitselectrical power to and from the first electric machine 56 by transferconductors 29, and the TPIM 19 similarly transmits electrical power toand from the second electric machine 72 by transfer conductors 31 tomeet the torque commands for the first and second electric machines 56and 72 in response to the motor torques T_(A) and T_(B). Electricalcurrent is transmitted to and from the ESD 74 in accordance with whetherthe ESD 74 is being charged or discharged.

The TPIM 19 includes the pair of power inverters (not shown) andrespective motor control modules (not shown) configured to receive thetorque commands and control inverter states therefrom for providingmotor drive or regeneration functionality to meet the commanded motortorques T_(A) and T_(B). The power inverters comprise knowncomplementary three-phase power electronics devices, and each includes aplurality of insulated gate bipolar transistors (not shown) forconverting DC power from the ESD 74 to AC power for powering respectiveones of the first and second electric machines 56 and 72, by switchingat high frequencies. The insulated gate bipolar transistors form aswitch mode power supply configured to receive control commands. Thereis typically one pair of insulated gate bipolar transistors for eachphase of each of the three-phase electric machines. States of theinsulated gate bipolar transistors are controlled to provide motor drivemechanical power generation or electric power regenerationfunctionality. The three-phase inverters receive or supply DC electricpower via DC transfer conductors 27 and transform it to or fromthree-phase AC power, which is conducted to or from the first and secondelectric machines 56 and 72 for operation as motors or generators viatransfer conductors 29 and 31 respectively.

FIG. 2 is a schematic block diagram of the distributed control modulesystem. The elements described hereinafter comprise a subset of anoverall vehicle control architecture, and provide coordinated systemcontrol of the exemplary hybrid powertrain described in FIG. 1. Thedistributed control module system synthesizes pertinent information andinputs, and executes algorithms to control various actuators to meetcontrol objectives, including objectives related to fuel economy,emissions, performance, drivability, and protection of hardware,including batteries of ESD 74 and the first and second electric machines56 and 72. The distributed control module system includes an enginecontrol module (hereafter ‘ECM’) 23, the TCM 17, a battery pack controlmodule (hereafter ‘BPCM’) 21, and the TPIM 19. A hybrid control module(hereafter ‘HCP’) 5 provides supervisory control and coordination of theECM 23, the TCM 17, the BPCM 21, and the TPIM 19. A user interface(‘UI’) 13 is operatively connected to a plurality of devices throughwhich a vehicle operator controls or directs operation of theelectromechanical hybrid powertrain. The devices include an acceleratorpedal 113 (‘AP’), an operator brake pedal 112 (‘BP’), a transmissiongear selector 114 (‘PRNDL’), and a vehicle speed cruise control (notshown). The transmission gear selector 114 may have a discrete number ofoperator-selectable positions, including the rotational direction of theoutput member 64 to enable one of a forward and a reverse direction.

The aforementioned control modules communicate with other controlmodules, sensors, and actuators via a local area network (hereafter‘LAN’) bus 6. The LAN bus 6 allows for structured communication ofstates of operating parameters and actuator command signals between thevarious control modules. The specific communication protocol utilized isapplication-specific. The LAN bus 6 and appropriate protocols providefor robust messaging and multi-control module interfacing between theaforementioned control modules, and other control modules providingfunctionality including e.g., antilock braking, traction control, andvehicle stability. Multiple communications buses may be used to improvecommunications speed and provide some level of signal redundancy andintegrity. Communication between individual control modules can also beeffected using a direct link, e.g., a serial peripheral interface(‘SPI’) bus (not shown).

The HCP 5 provides supervisory control of the hybrid powertrain, servingto coordinate operation of the ECM 23, TCM 17, TPIM 19, and BPCM 21.Based upon various input signals from the user interface 13 and thehybrid powertrain, including the ESD 74, the HCP 5 determines anoperator torque request, an output torque command, an engine inputtorque command, clutch torque(s) for the applied torque-transferclutches C1 70, C2 62, C3 73, C4 75 of the transmission 10, and themotor torques T_(A) and T_(B) for the first and second electric machines56 and 72. The TCM 17 is operatively connected to the hydraulic controlcircuit 42 and provides various functions including monitoring variouspressure sensing devices (not shown) and generating and communicatingcontrol signals to various solenoids (not shown) thereby controllingpressure switches and control valves contained within the hydrauliccontrol circuit 42.

The ECM 23 is operatively connected to the engine 14, and functions toacquire data from sensors and control actuators of the engine 14 over aplurality of discrete lines, shown for simplicity as an aggregatebi-directional interface cable 35. The ECM 23 receives the engine inputtorque command from the HCP 5. The ECM 23 determines the actual engineinput torque, T_(I), provided to the transmission 10 at that point intime based upon monitored engine speed and load, which is communicatedto the HCP 5. The ECM 23 monitors input from the rotational speed sensor11 to determine the engine input speed to the input shaft 12, whichtranslates to the transmission input speed, N_(I). The ECM 23 monitorsinputs from sensors (not shown) to determine states of other engineoperating parameters including, e.g., a manifold pressure, enginecoolant temperature, ambient air temperature, and ambient pressure. Theengine load can be determined, for example, from the manifold pressure,or alternatively, from monitoring operator input to the acceleratorpedal 113. The ECM 23 generates and communicates command signals tocontrol engine actuators, including, e.g., fuel injectors, ignitionmodules, and throttle control modules, none of which are shown.

The TCM 17 is operatively connected to the transmission 10 and monitorsinputs from sensors (not shown) to determine states of transmissionoperating parameters. The TCM 17 generates and communicates commandsignals to control the transmission 10, including controlling thehydraulic control circuit 42. Inputs from the TCM 17 to the HCP 5include estimated clutch torques for each of the clutches, i.e., C1 70,C2 62, C3 73, and C4 75, and rotational output speed, N_(O), of theoutput member 64. Other actuators and sensors may be used to provideadditional information from the TCM 17 to the HCP 5 for controlpurposes. The TCM 17 monitors inputs from pressure switches (not shown)and selectively actuates pressure control solenoids (not shown) andshift solenoids (not shown) of the hydraulic control circuit 42 toselectively actuate the various clutches C1 70, C2 62, C3 73, and C4 75to achieve various transmission operating range states, as describedhereinbelow.

The BPCM 21 is signally connected to sensors (not shown) to monitor theESD 74, including states of electrical current and voltage parameters,to provide information indicative of parametric states of the batteriesof the ESD 74 to the HCP 5. The parametric states of the batteriespreferably include battery state-of-charge, battery voltage (‘V_(BAT)’),battery temperature, and available battery power (‘P_(BAT)’), referredto as a range P_(BAT) _(—) _(MIN) to P_(BAT) _(MAX).

A brake control module (hereafter ‘BrCM’) 22 is operatively connected tofriction brakes (not shown) on each of the vehicle wheels 93. The BrCM22 monitors the operator input to the brake pedal 112 and generatescontrol signals to control the friction brakes and sends a controlsignal to the HCP 5 to operate the first and second electric machines 56and 72 based thereon.

Each of the control modules ECM 23, TCM 17, TPIM 19, BPCM 21, and BrCM22 is preferably a general-purpose digital computer comprising amicroprocessor or central processing unit, storage mediums comprisingread only memory (‘ROM’), random access memory (‘RAM’), electricallyprogrammable read only memory (‘EPROM’), a high speed clock, analog todigital (‘A/D’) and digital to analog (‘D/A’) circuitry, andinput/output circuitry and devices (‘I/O’) and appropriate signalconditioning and buffer circuitry. Each of the control modules has a setof control algorithms, comprising resident program instructions andcalibrations stored in one of the storage mediums and executed toprovide the respective functions of each computer. Information transferbetween the control modules is preferably accomplished using the LAN bus6 and SPI buses. The control algorithms are executed during preset loopcycles such that each algorithm is executed at least once each loopcycle. Algorithms stored in the non-volatile memory devices are executedby one of the central processing units to monitor inputs from thesensing devices and execute control and diagnostic routines to controloperation of the actuators, using preset calibrations. Loop cycles areexecuted at regular intervals, for example each 3.125, 6.25, 12.5, 25and 100 milliseconds during ongoing operation of the hybrid powertrain.Alternatively, algorithms may be executed in response to the occurrenceof an event.

The exemplary hybrid powertrain selectively operates in one of severaloperating range states that can be described in terms of an engine statecomprising one of an engine-on state (‘ON’) and an engine-off state(‘OFF’), and a transmission state comprising a plurality of fixed gearsand continuously variable operating modes, described with reference toTable 1, below.

TABLE 1 Engine Transmission Operating Applied Description State RangeState Clutches M1_Eng_Off OFF EVT Mode 1 C1 70 M1_Eng_On ON EVT Mode 1C1 70 G1 ON Fixed Gear Ratio 1 C1 70 C4 75 G2 ON Fixed Gear Ratio 2 C170 C2 62 M2_Eng_Off OFF EVT Mode 2 C2 62 M2_Eng_On ON EVT Mode 2 C2 62G3 ON Fixed Gear Ratio 3 C2 62 C4 75 G4 ON Fixed Gear Ratio 4 C2 62 C373

Each of the transmission operating range states is described in thetable and indicates which of the specific clutches C1 70, C2 62, C3 73,and C4 75 are applied for each of the operating range states. A firstcontinuously variable mode, i.e., EVT Mode 1, or M1, is selected byapplying clutch C1 70 only in order to “ground” the outer gear member ofthe third planetary gear set 28. The engine state can be one of ON(‘M1_Eng_On’) or OFF (‘M_Eng_Off’). A second continuously variable mode,i.e., EVT Mode 2, or M2, is selected by applying clutch C2 62 only toconnect the shaft 60 to the carrier of the third planetary gear set 28.The engine state can be one of ON (‘M2_Eng_On’) or OFF (‘M2_Eng_Off’).For purposes of this description, when the engine state is OFF, theengine input speed is equal to zero revolutions per minute (‘RPM’),i.e., the engine crankshaft is not rotating. A fixed gear operationprovides a fixed ratio operation of input-to-output speed of thetransmission 10, i.e., N_(I)/N_(O). A first fixed gear operation (‘G1’)is selected by applying clutches C1 70 and C4 75. A second fixed gearoperation (‘G2’) is selected by applying clutches C1 70 and C2 62. Athird fixed gear operation (‘G3’) is selected by applying clutches C2 62and C4 75. A fourth fixed gear operation (‘G4’) is selected by applyingclutches C2 62 and C3 73. The fixed ratio operation of input-to-outputspeed increases with increased fixed gear operation due to decreasedgear ratios in the planetary gears 24, 26, and 28. The rotational speedsof the first and second electric machines 56 and 72, N_(A) and N_(B)respectively, are dependent on internal rotation of the mechanism asdefined by the clutching and are proportional to the input speedmeasured at the input shaft 12.

In response to operator input via the accelerator pedal 113 and brakepedal 112 as captured by the user interface 13, the HCP 5 and one ormore of the other control modules determine torque commands to controlthe torque generative devices comprising the engine 14 and first andsecond electric machines 56 and 72 to meet the operator torque requestat the output member 64 and transferred to the driveline 90. Based uponinput signals from the user interface 13 and the hybrid powertrainincluding the ESD 74, the HCP 5 determines the operator torque request,a commanded output torque from the transmission 10 to the driveline 90,an input torque from the engine 14, clutch torques for thetorque-transfer clutches C1 70, C2 62, C3 73, C4 75 of the transmission10; and the motor torques for the first and second electric machines 56and 72, respectively, as is described hereinbelow.

Final vehicle acceleration can be affected by other factors including,e.g., road load, road grade, and vehicle mass. The operating range stateis determined for the transmission 10 based upon a variety of operatingcharacteristics of the hybrid powertrain. This includes the operatortorque request communicated through the accelerator pedal 113 and brakepedal 112 to the user interface 13 as previously described. Theoperating range state may be predicated on a hybrid powertrain torquedemand caused by a command to operate the first and second electricmachines 56 and 72 in an electrical energy generating mode or in atorque generating mode. The operating range state can be determined byan optimization algorithm or routine which determines optimum systemefficiency based upon operator demand for power, batterystate-of-charge, and energy efficiencies of the engine 14 and the firstand second electric machines 56 and 72. The control system managestorque inputs from the engine 14 and the first and second electricmachines 56 and 72 based upon an outcome of the executed optimizationroutine, and system efficiencies are optimized thereby, to manage fueleconomy and battery charging. Furthermore, operation can be determinedbased upon a fault in a component or system. The HCP 5 monitors thetorque-generative devices, and determines the power output from thetransmission 10 required in response to the desired output torque atoutput member 64 to meet the operator torque request. As should beapparent from the description above, the ESD 74 and the first and secondelectric machines 56 and 72 are electrically-operatively coupled forpower flow therebetween. Furthermore, the engine 14, the first andsecond electric machines 56 and 72, and the electromechanicaltransmission 10 are mechanically-operatively coupled to transfer powertherebetween to generate a power flow to the output member 64.

FIG. 3 details the system for controlling and managing torque and powerflow in a powertrain system having multiple torque generative devices,described with reference to the hybrid powertrain system of FIGS. 1 and2, and residing in the aforementioned control modules in the form ofexecutable algorithms and calibrations. The control system architecturecan be applied to any powertrain system having multiple torquegenerative devices, including, e.g., a hybrid powertrain system having asingle electric machine, a hybrid powertrain system having multipleelectric machines, and non-hybrid powertrain systems.

The control system architecture of FIGS. 3 depicts a flow of pertinentsignals through the control modules. In operation, the operator inputsto the accelerator pedal 113 and the brake pedal 112 are monitored todetermine the operator torque request (‘To req’). Operation of theengine 14 and the transmission 10 are monitored to determine the inputspeed (‘Ni’) and the output speed (‘No’). A strategic optimizationcontrol scheme (‘Strategic Control’) 310 determines a preferred inputspeed (‘Ni_Des’) and transmission operating range state (‘Hybrid RangeState Des’) based upon the output speed and the operator torque request,and optimized based upon other operating parameters of the hybridpowertrain, including battery power limits and response limits of theengine 14, the transmission 10, and the first and second electricmachines 56 and 72. The strategic optimization control scheme 310 ispreferably executed by the HCP 5 during each 100 ms loop cycle and each25 ms loop cycle.

The outputs of the strategic optimization control scheme 310 are used ina shift execution and engine start/stop control scheme (‘Shift Executionand Engine Start/Stop’) 320 to command changes in the transmissionoperation (‘Transmission Commands’) including changing the operatingrange state. This includes commanding execution of a change in theoperating range state if the preferred operating range state isdifferent from the present operating range state by commanding changesin application of one or more of the clutches C1 70, C2 62, C3 73, andC4 75 and other transmission commands. The present operating range state(‘Hybrid Range State Actual’) and an input speed profile (‘Ni_Prof’) canbe determined. The input speed profile is an estimate of an upcominginput speed and preferably comprises a scalar parametric value that is atargeted input speed for the forthcoming loop cycle. The engineoperating commands and torque request are based upon the input speedprofile during a transition in the operating range state of thetransmission.

A tactical control scheme (‘Tactical Control and Operation’) 330 isrepeatedly executed during one of the control loop cycles to determineengine commands (‘Engine Commands’) for operating the engine, includinga preferred input torque from the engine 14 to the transmission 10 basedupon the output speed, the input speed, and the operator torque requestand the present operating range state for the transmission. The enginecommands also include engine states including one of an all-cylinderoperating state and a cylinder deactivation operating state wherein aportion of the engine cylinders are deactivated and unfueled, and enginestates including one of a fueled state and a fuel cutoff state.

A clutch torque (‘Tcl’) for each clutch is estimated in the TCM 17,including the presently applied clutches and the non-applied clutches,and a present engine input torque (‘Ti’) reacting with the input member12 is determined in the ECM 23. An output and motor torque determinationscheme (‘Output and Motor Torque Determination’) 340 is executed todetermine the preferred output torque from the powertrain (‘To_cmd’),which includes motor torque commands (‘T_(A)’ and ‘T_(B)’) forcontrolling the first and second electric machines 56 and 72 in thisembodiment. The preferred output torque is based upon the estimatedclutch torque(s) for each of the clutches, the present input torque fromthe engine 14, the present operating range state, the input speed, theoperator torque request, and the input speed profile. The first andsecond electric machines 56 and 72 are controlled through the TPIM 19 tomeet the preferred motor torque commands based upon the preferred outputtorque. The output and motor torque determination scheme 340 includesalgorithmic code which is regularly executed during the 6.25 ms and 12.5ms loop cycles to determine the preferred motor torque commands.

The hybrid powertrain is controlled to transfer the output torque to theoutput member 64 and thence to the driveline 90 to generate tractivetorque at wheel(s) 93 to forwardly propel the vehicle in response to theoperator input to the accelerator pedal 113 when the operator selectedposition of the transmission gear selector 114 commands operation of thevehicle in the forward direction. Preferably, forwardly propelling thevehicle results in vehicle forward acceleration so long as the outputtorque is sufficient to overcome external loads on the vehicle, e.g.,due to road grade, aerodynamic loads, and other loads.

In operation, operator inputs to the accelerator pedal 113 and to thebrake pedal 112 are monitored to determine the operator torque request.Present speeds of the output member 64 and the input member 12, i.e., Noand Ni, are determined. A present operating range state of thetransmission 14 and present engine states are determined. Maximum andminimum electric power limits of the electric energy storage device 74are determined.

Blended brake torque includes a combination of the friction brakingtorque generated at the wheels 93 and the output torque generated at theoutput member 64 which reacts with the driveline 90 to decelerate thevehicle in response to the operator input to the brake pedal 112.

The BrCM 22 commands the friction brakes on the wheels 93 to applybraking force and generates a command for the transmission 10 to createa change in output torque which reacts with the driveline 90 in responseto a net operator input to the brake pedal 112 and the accelerator pedal113. Preferably the applied braking force and the negative output torquecan decelerate and stop the vehicle so long as they are sufficient toovercome vehicle kinetic power at wheel(s) 93. The negative outputtorque reacts with the driveline 90, thus transferring torque to theelectromechanical transmission 10 and the engine 14. The negative outputtorque reacted through the electromechanical transmission 10 can betransferred to the first and second electric machines 56 and 72 togenerate electric power for storage in the ESD 74.

The operator inputs to the accelerator pedal 113 and the brake pedal 112together with torque intervention controls comprise individuallydeterminable operator torque request inputs including an immediateaccelerator output torque request (‘Output Torque Request Accel Immed’),a predicted accelerator output torque request (‘Output Torque RequestAccel Prdtd’), an immediate brake output torque request (‘Output TorqueRequest Brake Immed’), a predicted brake output torque request (‘OutputTorque Request Brake Prdtd’) and an axle torque response type (‘AxleTorque Response Type’). As used herein, the term ‘accelerator’ refers toan operator request for forward propulsion preferably resulting inincreasing vehicle speed over the present vehicle speed, when theoperator selected position of the transmission gear selector 114commands operation of the vehicle in the forward direction, and asimilar reverse propulsion response when the vehicle operation iscommanded in the reverse direction. The terms ‘deceleration’ and ‘brake’refer to an operator request preferably resulting in decreasing vehiclespeed from the present vehicle speed. The immediate accelerator outputtorque request, the predicted accelerator output torque request, theimmediate brake output torque request, the predicted brake output torquerequest, and the axle torque response type are individual inputs to thecontrol system.

The immediate accelerator output torque request comprises an immediatetorque request determined based upon the operator input to theaccelerator pedal 113 and torque intervention controls. The controlsystem controls the output torque from the hybrid powertrain system inresponse to the immediate accelerator output torque request to causepositive acceleration of the vehicle. The immediate brake output torquerequest comprises an immediate braking request determined based upon theoperator input to the brake pedal 112 and torque intervention controls.The control system controls the output torque from the hybrid powertrainsystem in response to the immediate brake output torque request to causedeceleration of the vehicle. Vehicle deceleration effected by control ofthe output torque from the hybrid powertrain system is combined withvehicle deceleration effected by a vehicle braking system (not shown) todecelerate the vehicle to achieve the operator braking request.

The immediate accelerator output torque request is determined based upona presently occurring operator input to the accelerator pedal 113, andcomprises a request to generate an immediate output torque at the outputmember 64 preferably to accelerate the vehicle. The immediateaccelerator output torque request may be modified by torque interventioncontrols based on events that affect vehicle operation outside thepowertrain control. Such events include vehicle level interruptions inthe powertrain control for antilock braking, traction control andvehicle stability control, which can be used to modify the immediateaccelerator output torque request.

The predicted accelerator output torque request is determined based uponthe operator input to the accelerator pedal 113 and comprises an optimumor preferred output torque at the output member 64. The predictedaccelerator output torque request is preferably equal to the immediateaccelerator output torque request during normal operating conditions,e.g., when torque intervention controls is not being commanded. Whentorque intervention, e.g., any one of antilock braking, traction controlor vehicle stability, is being is commanded, the predicted acceleratoroutput torque request can remain the preferred output torque with theimmediate accelerator output torque request being decreased in responseto output torque commands related to the torque intervention.

The immediate brake output torque request and the predicted brake outputtorque request are both blended brake torque requests. Blended braketorque includes a combination of the friction braking torque generatedat the wheels 93 and the output torque generated at the output member 64which reacts with the driveline 90 to decelerate the vehicle in responseto the operator input to the brake pedal 112.

The immediate brake output torque request is determined based upon apresently occurring operator input to the brake pedal 112, and comprisesa request to generate an immediate output torque at the output member 64to effect a reactive torque with the driveline 90 which preferablydecelerates the vehicle. The immediate brake output torque request isdetermined based upon the operator input to the brake pedal 112, and thecontrol signal to control the friction brakes to generate frictionbraking torque.

The predicted brake output torque request comprises an optimum orpreferred brake output torque at the output member 64 in response to anoperator input to the brake pedal 112 subject to a maximum brake outputtorque generated at the output member 64 allowable regardless of theoperator input to the brake pedal 112. In one embodiment the maximumbrake output torque generated at the output member 64 is limited to −0.2g. The predicted brake output torque request can be phased out to zerowhen vehicle speed approaches zero regardless of the operator input tothe brake pedal 112. As desired, there can be operating conditions underwhich the predicted brake output torque request is set to zero, e.g.,when the operator setting to the transmission gear selector 114 is setto a reverse gear, and when a transfer case (not shown) is set to afour-wheel drive low range. The operating conditions whereat thepredicted brake output torque request is set to zero are those in whichblended braking is not preferred due to vehicle operating factors.

The axle torque response type comprises an input state for shaping andrate-limiting the output torque response through the first and secondelectric machines 56 and 72. The input state for the axle torqueresponse type can be an active state or an inactive state. When thecommanded axle torque response type is an active state, the outputtorque command is the immediate output torque. Preferably the torqueresponse for this response type is as fast as possible.

The predicted accelerator output torque request and the predicted brakeoutput torque request are input to the strategic optimization controlscheme (‘Strategic Control’) 310. The strategic optimization controlscheme 310 determines a desired operating range state for thetransmission 10 (‘Hybrid Range State Des’) and a desired input speedfrom the engine 14 to the transmission 10 (‘Ni Des’), which compriseinputs to the shift execution and engine operating state control scheme(‘Shift Execution and Engine Start/Stop’) 320.

A change in the input torque from the engine 14 which reacts with theinput member from the transmission 10 can be effected by changing massof intake air to the engine 14 by controlling position of an enginethrottle utilizing an electronic throttle control system (not shown),including opening the engine throttle to increase engine torque andclosing the engine throttle to decrease engine torque. Changes in theinput torque from the engine 14 can be effected by adjusting ignitiontiming, including retarding spark timing from a mean-best-torque sparktiming to decrease engine torque. The engine state can be changedbetween the engine-off state and the engine-on state to effect a changein the input torque. The engine state can be changed between theall-cylinder operating state and the cylinder deactivation operatingstate, wherein a portion of the engine cylinders are unfueled. Theengine state can be changed by selectively operating the engine 14 inone of the fueled state and the fuel cutoff state wherein the engine isrotating and unfueled. Executing a shift in the transmission 10 from afirst operating range state to a second operating range state can becommanded and achieved by selectively applying and deactivating theclutches C1 70, C2 62, C3 73, and C4 75.

The immediate accelerator output torque request, the predictedaccelerator output torque request, the immediate brake output torquerequest, the predicted brake output torque request, and the axle torqueresponse type are inputs to the tactical control and operation scheme330 to determine the engine command comprising the preferred inputtorque to the engine 14.

The tactical control and operation scheme 330 can be divided into twoparts. This includes determining a desired engine torque, and thereforea power split between the engine 14 and the first and second electricmachines 56 and 72, and controlling the engine states and operation ofthe engine 14 to meet the desired engine torque. The engine statesinclude the all-cylinder state and the cylinder deactivation state, anda fueled state and a deceleration fuel cutoff state for the presentoperating range state and the present engine speed. The tactical controland operation scheme 330 monitors the predicted accelerator outputtorque request and the predicted brake output torque request todetermine the predicted input torque request. The immediate acceleratoroutput torque request and the immediate brake output torque request areused to control the engine speed/load operating point to respond tooperator inputs to the accelerator pedal 113 and the brake pedal 112,e.g., to determine the engine command comprising the preferred inputtorque to the engine 14. Preferably, a rapid change in the preferredinput torque to the engine 14 occurs only when the first and secondelectric machines 56 and 72 cannot meet the operator torque request.

The immediate accelerator output torque request, the immediate brakeoutput torque request, and the axle torque response type are input tothe motor torque control scheme (‘Output and Motor TorqueDetermination’) 340. The motor torque control scheme 340 executes todetermine the motor torque commands during each iteration of one of theloop cycles, preferably the 6.25 ms loop cycle.

The present input torque (‘Ti’) from the engine 14 and the estimatedclutch torque(s) (‘Tcl’) are input to the motor torque control scheme340. The axle torque response type signal determines the torque responsecharacteristics of the output torque command delivered to the outputmember 64 and hence to the driveline 90.

The motor torque control scheme 340 controls motor torque commands ofthe first and second electric machines 56 and 72 to transfer a netcommanded output torque to the output member 64 of the transmission 10that meets the operator torque request. The control system architecturecontrols power flow among power actuators within a hybrid powertrain.The hybrid powertrain utilizes two or more power actuators to provideoutput power to an output member. Controlling power flow among the poweractuators includes controlling the input speed N_(I) from the engine 14,the input torque T_(I) from the engine, and the motor torques T_(A),T_(B) of the first and second electric machines 56, 72. Although in theexemplary embodiment described herein above, the hybrid powertrainutilizes the control system architecture to control power flow amongpower actuators including the engine 14, the ESD 74 and the first andsecond electric machines 56 and 72, in alternate embodiments the controlsystem architecture can control power flow among other types of poweractuators. Exemplary power actuators that can be utilized include fuelcells, ultra-capacitors and hydraulic actuators.

The control system architecture manages electric power within theexemplary powertrain system utilizing electric power limits. Thisincludes monitoring voltage (‘V_(BAT)’) and power (‘P_(BAT)’) of the ESD74. The control system architecture utilizes a method for managingelectric power within the powertrain system that includes establishingpredicted electric power limits, long-term electric power limits,short-term electric power limits, and voltage-based electric powerlimits. The method further includes determining a preferred input speedfrom the engine 14, a preferred input torque from the engine 14, apreferred engine state, and a preferred operating range state of thetransmission 10 utilizing the predicted electric power limits. Themethod further includes determining input torque constraints forconstraining input torque from the engine 14 and output torqueconstraints for constraining output torque T_(O) to the output member 64based upon the long-term electric power limits and the short-termelectric power limits. By constraining the output torque T_(O), a totalmotor torque T_(M), consisting of first and second motor torques T_(A)and T_(B) of the first and second electric machines 56 and 72,respectively, is also constrained based on the set of output torqueconstraints and the input torque T_(I) from the engine 14. In analternate embodiment, a set of total motor torque constraints can bedetermined based upon the long-term electric power limits and short-termelectric power limits, in addition to, or instead of the set of outputtorque constraints. The method further includes determining outputtorque constraints based upon the voltage-based electric power limits.

The predicted electric power limits comprise preferred battery outputlevels associated with preferred ESD 74 performance levels, that is, thepredicted electric power limits prescribe the desired operating envelopeof the ESD 74. The predicted electric power limits comprise a range ofbattery output power levels from a minimum predicted electric powerlimit (‘P_(BAT) _(—) _(MIN) _(—) _(PRDTD)’) to a maximum predictedelectric power limit (‘P_(BAT) _(—) _(MAX) _(—) _(PRDTD)’). Thepredicted electric power limits can comprise a more constrained range ofbattery output power levels than the long-term electric power limits andthe short-term electric power limits.

The long-term electric power limits comprise battery output power levelsassociated with operation of the ESD 74 while maintaining long-termdurability of the ESD 74. Operation of the ESD 74 outside the long-termelectric power limits for extended periods of time may reduce theoperational life of the ESD 74. In one embodiment, the ESD 74 ismaintained within the long-term electric power limits duringsteady-state operation, that is, operation not associated with transientoperation. Exemplary transient operations include tip-in and tip-out ofthe accelerator pedal 113, wherein transient acceleration operation isrequested. Maintaining the ESD 74 within the long-term electric powerlimits, allows the ESD 74 to provide functionality such as delivering ahighest power level that does not degrade operational life of the ESD74. The long-term electric power limits comprise a range of batteryoutput power levels from a minimum long-term electric power limit(‘P_(BAT) _(—) _(MIN) _(—) _(LT)’) to a maximum long-term electric powerlimit (‘P_(BAT) _(—) _(MAX) _(—) _(LT)’). The long-term electric powerlimits can comprise a more constrained range of battery output powerlevels than the short-term electric power limits.

The short-term electric power limits comprise ESD 74 output power levelsassociated with battery operation that does not significantly affectshort-term battery durability. Operation of the ESD 74 outside theshort-term electric power limits may reduce the operational life of theESD 74. Operating the ESD 74 within the short-term electric powerlimits, but outside the long-term electric power limits for shortperiods of time, may minimally reduce the operational life of the ESD74, however, does not result in large amounts of degraded operationalperformance to the ESD 74. In one embodiment, the ESD 74 is maintainedwithin the short-term electric power limits during transient operation.The short-term electric power limits comprise a range of battery outputpower levels from a minimum short-term electric power limit (‘P_(BAT)_(—) _(MIN) _(—) _(ST)’) to a maximum short-term electric power limit(‘P_(BAT) _(—) _(MAX) _(—) _(ST)’).

The voltage-based electric power limits comprise a range of batteryoutput power from a minimum voltage-based electric power limit (‘P_(BAT)_(—) _(MAX) _(—) _(VB)’) to a maximum voltage-based electric power limit(‘P_(BAT) _(—) _(MAX) _(—) _(VB)’) based on desired operating voltagesof the ESD 74. The minimum voltage-based electric power limit P_(BAT)_(—) _(MIN) _(—) _(VB) is a minimum amount of battery output power thatthe ESD 74 outputs before reaching a maximum voltage V_(BAT) _(—) _(MAX)_(—) _(BASE). The maximum voltage-based electric power limit P_(BAT)_(—) _(MAX) _(—) _(VB) is an estimated amount battery output power fromthe ESD 74 before reaching a minimum voltage V_(BAT) _(—) _(MIN) _(—)_(BASE). The minimum voltage V_(BAT) _(—) _(MIN) _(—) _(BASE) is aminimum permissible voltage for operating the battery withoutsignificantly affecting short-term battery durability. Outputting powerfrom the ESD 74 when the voltage levels of the ESD 74 are below theminimum V_(BAT) _(—) _(MIN) _(—) _(BASE) can cause degraded operationallife of the ESD 74.

The tactical control scheme 330 determines a set of tactical controlelectric power constraints based upon the short-term electric powerlimits and the long-term electric power limits. In particular, thetactical control scheme 330 sets the tactical control electric powerconstraints to the long-term electric power limits, when the batteryoutput power of the ESD 74 is within a preferred tactical controlbattery output power operating range, wherein the preferred tacticalcontrol battery output power operating range is defined based upon theshort-term electric power limits. When the battery output power isoutside the preferred tactical control battery output power operatingrange, the tactical control scheme 330 utilizes feedback control basedupon the battery output power and the short-term electric power limitsto modify the tactical control electric power constraints to controlbattery output power P_(BAT) within the preferred tactical controlbattery output power operating range.

The set of tactical control electric power constraints are utilized todetermine a set of input torque constraints for the tactical controlscheme 330. When the preferred input torque as determined by theoptimization function is within the set of input torque constraints, thetactical control scheme 330 requests the preferred input torque from theengine 14, and the engine 14 controls the input torque T_(I) to thepreferred input torque, e.g., by adjusting engine fueling and/oradjusting position of an engine throttle . When the preferred inputtorque is outside the set of input torque constraints, the tacticalcontrol scheme requests the violated constraint for input torque fromthe engine 14, and the engine 14 adjusts combustion timing to controlinput torque within the input torque constraints.

FIG. 4 details signal flow for the output and motor torque determinationscheme 340 for controlling and managing the output torque through thefirst and second electric machines 56 and 72, described with referenceto the hybrid powertrain system of FIGS. 1 and 2 and the control systemarchitecture of FIGS. 3 and constraints include the maximum and minimumavailable battery power limits (‘Pbat Min/Max’). The output and motortorque determination scheme 340 controls the motor torque commands ofthe first and second electric machines 56 and 72 to transfer a netoutput torque to the output member 64 of the transmission 10 that reactswith the driveline 90 and meets the operator torque request, subject toconstraints and shaping. The output and motor torque determinationscheme 340 preferably includes algorithmic code and predeterminedcalibration code which is regularly executed during the 6.25 ms and 12.5ms loop cycles to determine preferred motor torque commands (‘T_(A)’,‘T_(B)’) for controlling the first and second electric machines 56 and72 in this embodiment.

The output and motor torque determination scheme 340 determines and usesa plurality of inputs to determine constraints on the output torque,from which it determines the output torque command (‘To_cmd’). Motortorque commands (‘T_(A)’, ‘T_(B)’) for the first and second electricmachines 56 and 72 can be determined based upon the output torquecommand. The inputs to the output and motor torque determination scheme340 include operator inputs, powertrain system inputs and constraints,and autonomic control inputs.

The operator inputs include the immediate accelerator output torquerequest (‘Output Torque Request Accel Immed’) and the immediate brakeoutput torque request (‘Output Torque Request Brake Immed’).

The autonomic control inputs include torque offsets to effect activedamping of the driveline 90 (412), to effect engine pulse cancellation(408), and to effect a closed loop correction based upon the input andoutput speeds (410). The torque offsets for the first and secondelectric machines 56 and 72 to effect active damping of the driveline 90can be determined (‘Ta AD’, ‘Tb AD’), e.g., to manage and effectdriveline lash adjustment, and are output from an active dampingalgorithm (‘AD’) (412). The torque offsets to effect engine pulsecancellation (‘Ta PC’, ‘Tb PC’) are determined during starting andstopping of the engine 14 during transitions between the engine-on state(‘ON’) and the engine-off state (‘OFF’) to cancel engine torquedisturbances, and are output from a pulse cancellation algorithm (‘PC’)(408). The torque offsets for the first and second electric machines 56and 72 to effect closed-loop correction torque are determined bymonitoring input speed to the transmission 10 and clutch slip speeds ofclutches C1 70, C2 62, C3 73, and C4 75. When operating in one of themode operating range states, the closed-loop correction torque offsetsfor the first and second electric machines 56 and 72 (‘Ta CL’, ‘Tb CL’)can be determined based upon a difference between the input speed fromsensor 11 (‘Ni’) and the input speed profile (‘Ni_Prof’). When operatingin Neutral, the closed-loop correction is based upon the differencebetween the input speed from sensor 11 (‘Ni’) and the input speedprofile (‘Ni_Prof’), and a difference between a clutch slip speed and atargeted clutch slip speed, e.g., a clutch slip speed profile for atargeted clutch C1 70. The closed-loop correction torque offsets areoutput from a closed loop control algorithm (‘CL’) (410). Clutchtorque(s) (‘Tcl’) comprising clutch reactive torque range(s) for theapplied torque transfer clutch(es), and unprocessed clutch slip speedsand clutch slip accelerations of the non-applied clutches can bedetermined for the specific operating range state for any of thepresently applied and non-locked clutches. The closed-loop motor torqueoffsets and the motor torque offsets to effect active damping of thedriveline 90 are input to a low pass filter to determine motor torquecorrections for the first and second electric machines 56 and 72 (‘T_(A)LPF’ and T_(B) LPF’) (405).

A battery power function (‘Battery Power Control’) 466 monitors batterypower inputs to determine electric power constraints comprising maximummotor torque control electric power constraint (‘P_(BAT) _(—) _(MAX)_(—) _(MT)’) and a minimum motor torque control electric powerconstraint (‘P_(BAT) _(—) _(MIN) _(—) _(MT)’) that is input to anoptimization algorithm 440 minimum and maximum raw output torqueconstraints (‘To Min Raw’, ‘To Max Raw’) (440). Inputs to the batterypower function 466 include battery voltage (‘V_(BAT)’), battery power(‘P_(BAT)’), the maximum voltage V_(BAT) _(—) _(MAX) _(—) _(BASE), theminimum voltage V_(BAT) _(—) _(MIN) _(—) _(BASE), a maximum long-termelectric power limit (‘P_(BAT) _(—) _(MAX) _(—) _(LT)’), a minimumlong-term electric power limit (‘P_(BAT) _(—) _(MIN) _(—) _(LT)’), amaximum short term electric power limit (‘P_(BAT) _(—) _(MAX) _(—)_(ST)’), and minimum short term electric power limit (‘P_(BAT) _(—)_(MIN) _(—) _(ST)’). There is also a discrete input comprising a boostrequest (‘Boost Request’).

Other system inputs include the operating range state (‘Hybrid RangeState’) and a plurality of system inputs and constraints (‘System Inputsand Constraints’). The system inputs can include scalar parametersspecific to the powertrain system and the operating range state, and canbe related to speed and acceleration of the input member 12, outputmember 64, and the clutches. Other system inputs are related to systeminertias, damping, and electric/mechanical power conversion efficienciesin this embodiment. The constraints include maximum and minimum motortorque outputs from the torque machines, i.e., first and second electricmachines 56 and 72 (‘Ta Min/Max’, ‘Tb Min/Max’), and maximum and minimumclutch reactive torques for the applied clutches. Other system inputsinclude the input torque, clutch slip speeds and other relevant states.

Inputs including an input acceleration profile (‘Nidot_Prof’) and aclutch slip acceleration profile (‘Clutch Slip Accel Prof’) are input toa pre-optimization algorithm (415), along with the system inputs, theoperating range state, and the motor torque corrections for the firstand second electric machines 56 and 72 (‘T_(A) LPF’ and T_(B) LPF’). Theinput acceleration profile is an estimate of an upcoming inputacceleration that preferably comprises a targeted input acceleration forthe forthcoming loop cycle. The clutch slip acceleration profile is anestimate of upcoming clutch acceleration for one or more of thenon-applied clutches, and preferably comprises a targeted clutch slipacceleration for the forthcoming loop cycle. Optimization inputs (‘OptInputs’), which can include values for motor torques, clutch torques andoutput torques can be calculated for the present operating range stateand used in an optimization algorithm to determine the maximum andminimum raw output torque constraints (440) and to determine thepreferred split of open-loop torque commands between the first andsecond electric machines 56 and 72 (440′). The optimization inputs, themaximum and minimum battery power limits, the system inputs and thepresent operating range state are analyzed to determine a preferred oroptimum output torque (‘To Opt’) and minimum and maximum raw outputtorque constraints (‘To Min Raw’, ‘To Max Raw’) (440), which can beshaped and filtered (420). The preferred output torque (‘To Opt’)comprises an output torque that minimizes battery power subject to theoperator torque request. The immediate accelerator output torque requestand the immediate brake output torque request are each shaped andfiltered and subjected to the minimum and maximum output torqueconstraints (‘To Min Filt’, ‘To Max Filt’) to determine minimum andmaximum filtered output torque request constraints (‘To Min Req Filtd’,‘To Max Req Filtd’). A constrained accelerator output torque request(‘To Req Accel Cnstrnd’) and a constrained brake output torque request(‘To Req Brake Cnstrnd’) can be determined based upon the minimum andmaximum filtered output torque request constraints (425).

Furthermore, a regenerative braking capacity (‘Opt Regen Capacity’) ofthe transmission 10 comprises a capacity of the transmission 10 to reactdriveline torque, and can be determined based upon constraints includingmaximum and minimum motor torque outputs from the torque machines andmaximum and minimum reactive torques for the applied clutches, takinginto account the battery power limits. The regenerative braking capacityestablishes a maximum value for the immediate brake output torquerequest. The regenerative braking capacity is determined based upon adifference between the constrained accelerator output torque request andthe preferred output torque. The constrained accelerator output torquerequest is shaped and filtered and combined with the constrained brakeoutput torque request to determine a net output torque command. The netoutput torque command is compared to the minimum and maximum requestfiltered output torques to determine the output torque command(‘To_cmd’) (430). When the net output torque command is between themaximum and minimum request filtered output torques, the output torquecommand is set to the net output torque command. When the net outputtorque command exceeds the maximum request filtered output torque, theoutput torque command is set to the maximum request filtered outputtorque. When the net output torque command is less than the minimumrequest filtered output torque, the output torque command is set to theminimum request filtered output torque command.

Powertrain operation is monitored and combined with the output torquecommand to determine a preferred split of open-loop torque commandsbetween the first and second electric machines 56 and 72 that meetsreactive clutch torque capacities (‘T_(A) Opt’ and ‘T_(B) Opt’), andprovide feedback related to the preferred battery power (‘Pbat Opt’)(440′). The motor torque corrections for the first and second electricmachines 56 and 72 (‘T_(A) LPF’ and T_(B) LPF’) are subtracted todetermine open loop motor torque commands (‘T_(A) OL’ and ‘T_(B) OL’)(460).

The open loop motor torque commands are combined with the autonomiccontrol inputs including the torque offsets to effect active damping ofthe driveline 90 (412), to effect engine pulse cancellation (408), andto effect a closed loop correction based upon the input and clutch slipspeeds (410), to determine the motor torques T_(A) and T_(B) forcontrolling the first and second electric machines 56 and 72 (470). Theaforementioned steps of constraining, shaping and filtering the outputtorque request to determine the output torque command which is convertedinto the torque commands for the first and second electric machines 56and 72 is preferably a feed-forward operation which acts upon the inputsand uses algorithmic code to calculate the torque commands.

The system operation as configured leads to determining output torqueconstraints based upon present operation and constraints of thepowertrain system. The operator torque request is determined based uponoperator inputs to the brake pedal and to the accelerator pedal. Theoperator torque request can be constrained, shaped and filtered todetermine the output torque command, including determining a preferredregenerative braking capacity. An output torque command can bedetermined that is constrained based upon the constraints and theoperator torque request. The output torque command is implemented bycommanding operation of the torque machines. The system operationeffects powertrain operation that is responsive to the operator torquerequest and within system constraints. The system operation results inan output torque shaped with reference to operator drivability demands,including smooth operation during regenerative braking operation.

The optimization algorithm (440, 440′) comprises an algorithm executedto determine powertrain system control parameters that are responsive tothe operator torque request that minimizes battery power consumption.The optimization algorithm 440 includes monitoring present operatingconditions of the electromechanical hybrid powertrain, e.g., thepowertrain system described hereinabove, based upon the system inputsand constraints, the present operating range state, and the availablebattery power limits. For a candidate input torque, the optimizationalgorithm 440 calculates powertrain system outputs that are responsiveto the system inputs comprising the aforementioned output torquecommands and are within the maximum and minimum motor torque outputsfrom the first and second electric machines 56 and 72, and within theavailable battery power, and within the range of clutch reactive torquesfrom the applied clutches for the present operating range state of thetransmission 10, and take into account the system inertias, damping,clutch slippages, and electric/mechanical power conversion efficiencies.Preferably, the powertrain system outputs include the preferred outputtorque (‘To Opt’), achievable torque outputs from the first and secondelectric machines 56 and 72 (‘Ta Opt’, ‘Tb Opt’) and the preferredbattery power (‘Pbat Opt’) associated with the achievable torqueoutputs.

FIGS. 5 and 6 graphically depicts operation of the power boost function466 during transitions between the engine-off state and the engine-onstate, described with reference to the powertrain system describedherein. FIG. 5 shows executing an engine autostart operating state(‘AUTOSTART’), and FIG. 6 shows executing an engine autostop operatingstate (‘AUTOSTOP’). A maximum boost electric power limit and a minimumboost electric power limit, preferably comprising the inputs comprisingthe maximum short term electric power limit (‘P_(BAT) _(—) _(MAX) _(—)_(ST)’) and the minimum short term electric power limit (‘P_(BAT) _(—)_(MIN) _(—) _(ST)’), are shown. The maximum long-term electric powerlimit (‘P_(BAT) _(—) _(MAX) _(—) _(LT)’), the minimum long-term electricpower limit (‘P_(BAT) _(—) _(MIN) _(—) _(LT)’) are also plotted. Amaximum adjusted electric power limit (‘P_(BAT) _(—) _(MAX) _(—)_(ADJ)’), and a minimum adjusted electric power limit (‘P_(BAT) _(—)_(MIN) _(—) _(ADJ)’) are depicted in terms of battery output power inkilowatts (‘Battery Power [kw]’) over time (‘Time [Seconds]’). Positivepower values refer to discharge values in which motors of the first andsecond electric machines 56 and 72 produce a positive output torquecausing discharging of the ESD 74. Negative power values refer to chargevalues in which motors of the first and second electric machines 56 and72 produce a negative output torque causing charging of the ESD 74. Theboost request signal (‘BOOST REQUEST’) is depicted as being eitheractive (‘ACTIVE’) or inactive (‘INACTIVE’) over time. When the boostrequest signal is active, the engine is in one of the autostartoperating mode and autostop operating mode.

As shown in FIGS. 5 and 6, the boost function 466 increases anddecreases the minimum and maximum adjusted electric power limits overtime in response to changes in the boost request signal, therebyinhibiting rapid torque changes due to rapid changes in the adjustedelectric power limits. When the boost request signal is active, theboost function 466 determines the maximum adjusted electric power limitbased upon a function that increases the maximum adjusted electric powerlimit to the maximum autostart electric power limit at a predeterminedrate. Further, when the boost request signal is active, the boostfunction 466 determines the minimum adjusted electric power limit basedupon a function that decreases the minimum adjusted electric power limitto the minimum autostart electric power limit at a predetermined rate.

When the boost request signal is inactive, the power boost function 466determines the maximum adjusted electric power limit based upon afunction that decreases the maximum adjusted electric power limit to themaximum long-term electric power limit at a predetermined rate. When thebattery output power P_(BAT) is greater than the maximum long-termelectric power limit, for example, when exiting the autostart operatingmode, the power boost function 466 sets the maximum adjusted electricpower limit to the actual battery output power P_(BAT) and subsequentlydecreases the maximum adjusted electric power limit at a calibrated rateuntil the maximum adjusted electric power limit meets the maximumlong-term electric power limit. Further, when the boost request signalis inactive, the power boost function determines the minimum adjustedelectric power limit based upon a function that increases the minimumadjusted electric power limit to the minimum autostart electric powerlimit at a predetermined rate. When the actual battery output powerP_(BAT) is less than the minimum long-term electric power limit, forexample, when exiting the autostop engine operating mode, the powerboost function 466 sets the minimum adjusted electric power limit to theactual battery output power P_(BAT) and increases the minimum adjustedelectric power limit at a calibrated rate until the minimum adjustedelectric power limit equals the minimum long-term electric power limit.Thus, at any point in time the electric power constraints comprising themaximum motor torque control electric power constraint (‘P_(BAT) _(—)_(MAX) _(—) _(MT)’) and the minimum motor torque control electric powerconstraint (‘P_(BAT) _(—) _(MIN) _(—) _(MT)’) can be determined duringoperation of the powertrain, and can comprise the maximum short termelectric power limit (‘P_(BAT) _(—) _(MAX) _(—) _(ST)’) and the minimumshort term electric power limit (‘P_(BAT) _(—) _(MIN) _(—) _(ST)’), themaximum long-term electric power limit (‘P_(BAT) _(—) _(MAX) _(—)_(LT)’) and the minimum long-term electric power limit (‘P_(BAT) _(—)_(MIN) _(—) _(LT)’), or the maximum adjusted electric power limit(‘P_(BAT) _(—) _(MAX) _(—) _(ADJ)’), and the minimum adjusted electricpower limit (‘P_(BAT) _(—) _(MIN) _(—) _(ADJ)’), depending upon whetherentering or exiting the autostart operating mode, or entering or exitingthe autostop operating mode, or during one of the autostart or autostopoperating modes.

The disclosure has described certain preferred embodiments andmodifications thereto. Further modifications and alterations may occurto others upon reading and understanding the specification. Therefore,it is intended that the disclosure not be limited to the particularembodiment(s) disclosed as the best mode contemplated for carrying outthis disclosure, but that the disclosure will include all embodimentsfalling within the scope of the appended claims.

1. Method for controlling a powertrain system comprising an enginecoupled to an input member of a transmission operative to transmit powerbetween the input member, a torque machine and an output member, thetorque machine connected to an energy storage device, the engineselectively operative in engine states comprising an engine-on state andan engine-off state, the method comprising: determining a first powerrange for output power of the energy storage device; commanding theengine to transition from a first engine state to a second engine state;and expanding the first power range of the energy storage device andcontrolling the torque machine based upon the expanded power range ofthe energy storage device during the transition from the first enginestate to the second engine state.
 2. The method of claim 1, furthercomprising expanding the first power range of the energy storage deviceuntil an electric power limit defining the power range substantiallymeets a set of boost electric power limit.
 3. The method of claim 1,further comprising expanding the first power range over time at acalibrated rate.
 4. The method of claim 1, further comprising: expandingthe first power range of the energy storage device; and controlling thetorque machine based upon the expanded power range of the energy storagedevice subsequent to the transition from the first engine state to thesecond engine state.
 5. The method of claim 4, further comprisingcontracting the expanded power range of the energy storage device untilcontracted power range substantially meets the first power range.
 6. Themethod of claim 5, wherein the first power range is based upon long-termbattery durability.
 7. The method of claim 4, further comprising:setting a power limit to the first power range when the transition fromthe first engine state to the second engine state is completed; andcontracting the power range subsequent to setting the electric powerlimit to the first power range.
 8. The method of claim 4, furthercomprising contracting the power range of the energy storage device overtime at a calibrated rate.
 9. The method of claim 1, further comprisingcontrolling output torque of the output member within a set of outputtorque constraints based upon the power range of the energy storagedevice.
 10. Method for controlling a powertrain system comprising anengine, a second torque machine, a transmission device and an energystorage device, the transmission device operative to transfer powerbetween the engine, the second torque machine, and an output member togenerate an output torque, the method comprising: monitoring outputpower of the energy storage device; monitoring the engine for anautostart operating state; determining a maximum electric power limitfor output power of the energy storage device; enabling electric powerboost when the engine is in the autostart operating engine operatingstate; and increasing the maximum electric power limit when electricpower boost is enabled.
 11. The method of claim 10, further comprisingincreasing the maximum electric power limit over time at a calibratedrate until the maximum electric power limit substantially meets amaximum boost electric power limit.
 12. The method of claim 10, furthercomprising: disabling electric power boost when the engine is not in theautostart operating engine operating state; and decreasing the maximumelectric power limit when electric power boost is disabled.
 13. Themethod of claim 12, further comprising decreasing the maximum electricpower limit over time at a calibrated rate until the maximum electricpower limit meets the maximum long-term electric power limits.
 14. Themethod of claim 13, wherein the long-term electric power limits arebased upon long-term battery durability.
 15. Method for controlling apowertrain system comprising an engine, a second torque machine, atransmission device and an energy storage device, the transmissiondevice operative to transfer power between the engine, the second torquemachine, and the output member to generate an output torque, the methodcomprising: monitoring output power of the energy storage device;monitoring the engine for an autostop operating state; determining aminimum electric power limit for output power of the energy storagedevice; enabling electric power boost when the engine is in the autostopoperating state; and decreasing the minimum electric power limit whenelectric power boost is enabled.
 16. The method of claim 15, furthercomprising decreasing the minimum electric power limit over time at acalibrated rate until the minimum electric power limit substantiallymeets a minimum boost electric power limit.
 17. The method of claim 15,further comprising: disabling electric power boost when the engine isnot in the autostop operating state; and increasing the minimum electricpower limit when electric power boost is disabled.
 18. The method ofclaim 17, further comprising increasing the maximum electric power limitover time at a calibrated rate until the maximum electric power limitmeets the maximum long-term electric power limits.